I think a problem with danger zones is that 5e's rest mechanics are ill suited to a videogame. If a player enters a danger zone, uses a short rest after the first two encounters, then in the third uses up the rest of their resources and after that they have a boss encounter they could enter that encounter drained of resources and unable to continue. Then what? A DM could fail forward something like that, but on a computer the best case scenario is they reload a save from three to four hours earlier and start over. That would just suck, for a lot of people thats uninstall and write a negative review territory.
If Danger zones are limited then they could always be placed in scenarios where fail forwarding is accepted, but in general for a long form game its not good for failure to be seeded hours and hours in advance with the player unable to see they've already lost.
